Dang, that is too bad. Mine seems to eat everything, however I bought a pair and lost one for the same reason.
There is a chance he is sick, because a healthy one should eat about anything especially frozen foods or live blackworms.
Look for signs of disease and QT if necessary.
QT can be as small as a 5 gallon bucket with airstone and heater in a pinch for a fish that small, with lots of water changes of course.